1. Field of the Invention
The present invention relates to multiple-capacitive-sensor controllers, and more particularly, to multiple-capacitive-sensor controllers containing general purpose input-output ports that can be shared by an LED driver and a capacitive touch detector.
2. Description of Related Art
Multiple-capacitive-sensor controllers are well known in the art and are an integral part of a sensor that uses the properties of capacitors to detect physical distance from the user or touches by the user. In addition to being a pure sense device, most multiple-capacitive-sensor controllers also contain input-output ports that can be used to control Light Emitting Diodes (LED).
Touch sensors such as capacitive buttons are often used in devices to allow the user to control the devices by approaching or touching them. LED drivers are often used to facilitate a response to the proximity of the user or touches by the user. Therefore, it would reduce the number of components and system cost if the multiple-capacitive-sensor controllers could also be used to control the LEDs.
FIG. 1 depicts a simplified circuit diagram of a system containing a multiple-capacitive-sensor controller 101 that is typical of the prior art. The multiple-capacitive-sensor controller 101 contains multiple I/O ports. Each I/O port can be configured as either a capacitive sensor pin or an LED driver. A capacitive sensor pin 102, after configuration, will have a capacitive sensor 104 connected to a pad 106. Pad 106 is then connected to a capacitive element 108. When a user interacts with capacitive element 108 through physical means such as approaching or touching it, the capacitive value of capacitive element 108 will change. Capacitive sensor 104 detects the capacitance change, allowing the system to react to the user interaction accordingly. An LED driver pin 110, after configuration, will have an LED Driver 112 connected to pad 116, which is connected to LED 114. This allows the system to use the capacitive sensor controller to control the LEDs.
However, the single sensor controller solution still requires one I/O port per function. Thus, it is not the most efficient solution in terms of system area and cost. For example, the prior art multiple capacitive sensor controller will need to have 10 I/Os if the system needs 5 capacitive inputs and 5 LED drivers. Accordingly, being able to use a single I/O for both capacitive input and LED driver functionalities reduces the I/O port requirement of the sensor controller. Using the present invention, a multiple capacitive sensor controller that needs to handle 5 capacitive inputs and 5 LED drivers will only need 6 I/O ports: 5 I/O ports to handle the capacitive inputs and LED drivers and 1 bias driver port.